Alternating-current block-signal system.



ALTERNATING CURRENT BLOCK SIGNAL SYSTEM.

APPLICATION FILED PEBJI, 1905.

W2 S Q12 T M W12 G. D. EHRET.

[F U o O H (Xv-100 O Patented Jan. 26, 1915.

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THE NORRIS PETERS 60.. PHQTo-LITHQ. WASHING TON. D. c.

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wq B 113 G. D. EHRET. ALTERNATING CURRENT BLOCK SIGNAL SYSTEM.

APPLICATION FILED IBBJI, 1905. 1,12 23, Patented Ja1L26, 1915.

2 SHEETS-SHEET 2.

THE NORRIS PETERS CO. FHGm-LITHQ. WASHINGTON. D. C.

CORNELIUS D. EHRET, OF ARDMORE, PENNSYLVANIA.

ALTERNATING-CURRENT BLOCK-SIGNAL SYSTEM.

Specification of Letters Patent.

Patented Jan. 26, 1915.

Application filed February 11, 1905. Serial No. 245,217.

To all whom it may concern Be it known that I, CORNELIUS D. Ermn'r, acitizen of the United States, residing at Ardmore, in the county ofMontgomery and State of Pennsylvania, have invented a new and useful.Alternating-Current Block-Signal System, of which the following is aspecification.

My invention relates to signaling systems, more especially thoseemployed in connection with steam or electric railways to indicate thecondition of the track in advance of the train or car.

I t is the object of my invention to provide a signal system wherein theusual relays and other contact devices are dispensed with in order toobviate the troubles attendant upon such types of apparatus.

It is the object of my invention to provide signaling apparatusdistributed along tracks of many miles in length, the energy beingsupplied from a central power station. The energy is preferably of thehigh tension alternating current kind which is reduced in pressure foruse on the track circuits.

It is the object of my invention to provide also motor operated signals,the motors being preferably of the commutatorless type; and it is thefurther object of my in vention to provide means whereby a single motormay operate to display both home and distant signals.

For an illustration of several of the numerous forms my invention maytake, reference is to be had to the accompanying drawing, in whichFigure 1 is a diagrammatic view of the circuits for a clock signalsystem in which a home signal only is operated. Fig. 2 is adiagran'n'natic view of the circuit arrangements in which both home anddistance signals are displayed. Fig. 3 is a diagrammatic view of circuitarrangements in which a single phase current is supplied. Fig. 4;illustrates a simple means of interconnecting a sei'naphore arm orsignal mechanism with a switch S, for use in the system shown in Fig.Fig. 5 is a diagram of a modified circuit arrangement.

Similar reference characters refer to similar parts throughout thedrawing.

Referring to Fig. 1, 1, 2, and 3 represent the three conductors of ahigh tension two phase alternating current supply circuit, preferably ofconstant potential, a generating station being installed at intervals ofsay 100 miles along the railroad, each station supplying current to adistance of 50 miles in both directions. The pressure on this supplycircuit may be made many thousands of volts as is commonly practised inlong distance power transmission. L and 5 represent the two rails of asingle track railroad, the direction of travel being assumed to be thatindicated by the arrow. The track is divided into blocks, as A, B, C, D,at desired intervals by the insertion of the insulating material 6, asis the common practice in block systems. At the entrance to each blockis installed signal apparatus to indicate the condition of the block tothe engineer or motorman on the train or car about to enter such block.At the end of each block, that is, at the right hand end as viewed inFig. 1, there is installed a step down transformer T, preferably of theconstant potential type, for impressing upon the track circuit a verylow potential alternating current. 79 and 8 represent the primary andsecondary wind ings respectively of such step down transformers. Fromeach terminal of the secondary winding .9, connection is made byconductors 7 and 8 with the two track rails. 9 represents anon-inductive resistance whose purpose is to prevent a complete shortcircuiting of the secondary winding 8 of each of the step downtransformers when the track rails are short circuited by the wheels andaxles of a train or car. These resistances 9 are made as small aspossible and yet great enough to prevent overheating of the transformerT in the case where a train or car should remain indefinitely in ablock- At the entrance to each block is installed an alternating currentmotor, preferably of the induction or asynchronous type, in which therotor or secondary carries a closed circuited winding without commutatoror contact device of any sort. These motors are well known in the art ofpower transmission. In the drawings the rotor of said motor isrepresented by 1* while the stator or primary windings in Figs. 1 and 2,are represented by to and 10 to indicate that they are traversed bycurrent from the different phases of the supply circuit. Each of thesewindings produces a component of the rotary magnetic field upon whichthe operation of the motor depends. An inspection of Figs. 1 and 2 willshow that the track circuits of neighboring blocks are traversed bycurrent from the different phases of the supply circuit. Thus in Fig. lthe track circuit of the block A is supplied with current from the phase1, 3, of the supply circuit; block B by current from the phase i l, 2;block C by current from the phase 1, 3

connected to the terminals of the secondary s of the step downtransformer, supplying current to the neighboring block to the rear. Itis thus seen that the stator windings are traversed by two phasecurrents, the current of one phase derived from the track circuit of theblock whose condition the motor is to indicate, while the other istraversed by current of another phase supplied at the end of theneighboring block to the rear. As well understood in the art of powertransmission, these dephased stator currents will cause the rotor torotate and perform mechanical work. Since however, the rotor of eachmotor must start from rest, (a condition attended by very small torquewhen the rotor winding has as low resistance as possible, and as is thepractice in power work where the rotor is torotate continuously andoperate at the highest electrical eificiency) and since it must produceits maximum torque at starting, I design the rotor winding so that itshall have a higher resistance than would be consistent with highefficiency in ordinary power work. To this end of securing high torqueat starting, the rotor is wound with higher resistance conductor than iscommon in power practice, or the rotor is wound with low resistanceconductor, as in power practice, and maintained in circuit therewith isan additional resistance whereby the resistance of the entire rotorwinding is maintained relatively high. The result is a high torque atstarting and throughout the range of move ment of the rotor.

Directly connected to the rotor shaft is the target, semaphore, disk, orother device represented by 10, whose extent of travel is limited by thestops 11 and 12. WV represents a weight or equivalent means for givingthe semaphore or target 10 a bias toward the danger position, namely thehorizontal position, as shown at the entrance to block C, (Fig. 1). Itis to be understood, however, that instead of directly connecting thesemaphore or target 10 to the rotor shaft, any suitable intermediategearing may be employed, in order that the rotor may make a plurality ofrevolutions during the move ment of the semaphore or target 10 from oneof its indicating positions to another.

The operation of the system shown in Fig. 1 is as follows :When thetracks are clear the motors are energizedby the cooperation of thepolyphase currents in windresultant greatly decreased or zero torque ofthe rotor r so that the weight N rotates the semaphore or target 10 tohorizontal position, thus indicating danger is in the block C. Similarlyshould a fault occur anywhere between. the supply conductors 1, 3, andthe rails at the end of the block C, or if a rail should be removed orbroken, the

winding 10 of the motor at entrance to block C will be robbed of currentwith resultant movement of target 10 to danger position. With a train orcar bridging the rails of block (1 the non-inductive resistance 9 at theend of block C prevents undue heating of the step down transformer T atthat point which continues to maintain requisite current through thestator winding w of the motor at the entrance to block D. When the trainor car 13 has moved on to block I), the target 10, at the entrance toblock D moves to danger position because stator winding 10 of the motorat that point is robbed of current. hen thecar or train has passed on toblock D, stator windin 4.0 of the motor at the entrance to block isagain energized, with resultant rotation of rotor 7', which causes thesemaphore or target 10 to move to safety position as indicated byextending downwardly at an angle as shown, for example, at the entranceto block B. 7

Referring to Fig. 2, the circuit arrangements are identical with thoseof Fig. 1, except that provision is made for displaying both home anddistant signals, that is, displaying by .the home signal the conditionof the block immediately in advance, and by the distant signal thecondition of the second block in advance. To. this end a reversingswitch S isv inserted between the secondary s of'each step downtransformer T and the track rails. As shown in Fig. 2 the two blades ofthe reversing switch are pivoted on the pair of contacts nearest therails and joined by a bar of insulating material, The lower ends of theswitch levers are adapted to cooperate with four contacts'incommunication with the secondary s of each step down transformer T. Eachswitch S is mechanically connected through any suitable means such as asystem of levers or gearing with the semaphore or target 10, which inFig. 2 is adapted to assume any one of three positions to indicatesafety,

warning, or danger. The switch S therefore assumes any one of the three,different positions according to the position of the semaphore arm 10.

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As shown in Fig. 4, semaphore arm 10 has pivoted thereto at 17 the rod16 which is pivoted at its lower end at 18 to one arm of the bell cranklever 19. The bell crank 19 is pivoted at 20 to the base or frame of theapparatus. At 21 the rod 22 is pivoted to the bell crank 19 and at 23 toa connection with the insulating bar connecting the two levers of theswitch S. As the semaphore arm 10 assumes different positions the switchS assumes different positions and cooperates with the contactshereinafter referred to.

The block D being clear the rotor r of the motor at the entrance toblock D is rotated in a counter clockwise direction until the target 10has come into engagement with the stop 11. During this movement theweight W has been elevated through a certain distance. The tendency istherefore for the semaphorearm to come to horizontal position ondecrease of torque in the motor. -With the arm or disk 10 in positionabove horizontal as shown at the entrance to block D the levers of theswitch S are in engagement with the two contacts to the right.

When a train or car 13 is'bridging the rails of the block C, the statorwinding w of the motor at the entrance to block C is robbed of currentwith the result that the semaphore arm 10 is moved to horizontalposition by the weight W which has been permitted to move to its lowestposition. As the semaphore arm has assumed this horizontal position, thelevers of the switch S at the end of the block B have been moved intoengagement with the two middle contacts, the result being the relativereversal of current in the track circuit of block B from what itnormally is. In other words the current in the stator winding 10 of themotor at the entrance to block B has been relatively reversed, so thatthe direction of rotation of the magnetic field produced by the twowindings Q02 and 10 has been reversed, with resultant reversal indirection of rotation of the rot-or 1' of this motor at the entrance toblock B. In consequence the semaphore 10 is rotated to a position belowhorizontal until it engages the stop 12. During such rotation the weightW has been elevated a certain distance. In rotating to this position thesemaphore arm 10 at the entrance to block B has shifted the switch S atthe end of block A so that the levers engage the two contacts to theleft. The result is that the current in the track circuit of block A isin normal direction, the same as if the target 10, at entrance to blockB, were in safety position, as shown in the entrance to block D. Thisbeing so, the torque in the motor at the entrance to block A is such asto keep the semaphore arm 10 in safety position against the stop 11.From this arrangement it follows that when nearing the end of block A anengineer or motorman is warned by the position of the semaphore arm 10at the entrance of block B that block B is clear but that there is atrain or fault in block C. When the train 13 7 rent in the track circuitof block C, resulting in shifting the semaphore arm 10 at the entranceto block C to warning position, below the horizontal. In so doing theswitch S at the end of block B is shifted to the left, thus returningthe current in the track circuit of block B to normal direction, thuscausing the semaphore arm 10 at the entrance to block B to be rotatedagainst the stop 11 to indicate safety in block B. In moving from stop12 to stop 11, the arm 10 at the entrance to block B moves the switch tothe extreme right, thus momentarily reversing the relative direction ofcurrent in the track circuit of block A and finally reestablishing it innormal direction when the arm 10 has come into engagement with the stop11 at the entrance to block B. The result is that the semaphore arm 10at the entrance of block A does not change its position, because thereversal of current in the track circuit of the block A is onlymomentary.

Referring to Fig. 3, 14: and 15 are the conductors of a single phasehigh tension, preferably constant potential, supply circuit. A step downtransformer T, and induction or asynchronous motor and a non-inductiveresistance 9 is provided at the entrance to each block as in the case ofFigs. 1 and 2. To effectively produce a rotating field in each motor,two stator windings, 1/1 and w I are provided and traversed by currentswhich are dephased with respect to each other. The windings w areconnected through non-inductive resistances F, across the secondaries sof the step down transformers T. Between the windings 10 and the railsmay be inserted an inductance winding L to produce a lagging current inthe windings 00 The current in the windings w" is practically in phasewith the electro-motive force of the secondaries 5, while the current inthe windings w lags behind such electro-motive force because of theinductance L. In cases where the inductance of the rails is notsufficient to produce the necessary lagging current, the additionalinductance L may be provided to secure the proper amount of lag. Thewindings v.0" and 20 being traversed by dephased currents, the motor atthe entrance to each block becomes in effect a polyphase motor as in thecases of Figs. 1 and 2. The inductance L may be omitted, and thenoninductive resistances 9 may be replaced by suitable inductancewindings.

The operation of the system shown in Fig. 3 is the same as that shown inFig. 1, that is, when the windings w are robbed of current, due to anyfault in a block or the presence of a train in a block, the weights IVrotate the semaphore arms 10 against the stops 11, indicating danger.WVhen the windings w are again energized, the torque of the rotors rovercomes the weights IV and rotates the arms 10 against the stops 12 toindicate safety.

Making the rotor windings or the circuits of the rotor windings ofrelatively high resistance serves the additional useful purpose ofreducing the amount of current traversing the rotor windings or theircircuits when'the rotors are at either safety or warn ing positions,which they frequently occupy for an indefinite length of time.

In Figs. 1 and 2 condensers is may be inserted in the track circuits tocompensate for any self induction effects which may be caused by theiron rails. The presence of these condensers is unnecessary unless the rlagging effect iaused by the rails becomes serious.

Inasmuch as it is desirable to have a very low potential. current in thetrack circuits while it is desirable to have a current of moderatepotential in the stator windings 0.0 Q0 10 and w, the secondaries s ofthe transformers T of all the figures may be wound in sections so that atap may be taken 05 to supply a low potential current to the trackcircuits, while the stator windings connected to such secondaries 8 maybe subjected to the full potential difference developed by suchsecondaries. To this end the conductors 7 may be connected at one end toa track rail and at the other end to the tap in the secondaries s of thetransformers T, whereby a very low potential is impressed upon the trackcircuits. Similar taps may be taken from the secondaries s of thetransformers T of Figs. 2 and 3 for the same purpose. In Fig. 2 thecontacts of the switches S would be connected to such conductors 7 whileone stator winding of each motor would be subjected to the fullpotential of the secondary s. In Fig. 3 a similar arrangement would bemade, the stator windings and the noninductive resistances F beingsubjected to the full potential of the secondaries s. In order that thestator windings connected with the track circuits at the beginning ofeach block shall be traversed by current of moderate potential, a stepup transformer T may intervene between each track circuit and theassociated stator winding, as shown in Fig. 5.

Though only a single track road has been shown in each of the figures ofthe drawin s, it is to be understood that any number of tracks may besupplied from, the same supply conductors l, 2, 3, or 14;, 15. Andthough the target operating motors are shown at the entrance to eachblock, it is to be understood that they may be placed at any othersuitable position 'to, constitute overlaps when it is desired thattraflic shall be in both directions on a single track.

Since it is desirable to have the potential of the current in the trackcircuits of all the blocks approximately the same, and since thepotential of the supply circuits diminishes as the distance from thegenerating stations becomes greater, the ratios of transformation of thetransformers T may change as the distance from the generating stationchanges, in order that the secondaries 8 may all deliver current atuniform potential. Or the energy supplied by the high potential circuitmay be stepped down to lower potential and supplied to local supplycircuits intervening between the high tension supply circuits and thetransformers T. Such local supply circuits may be relatively short inlength and supply current at proper potential to groups of b ocks.

From the foregoing descriptions it is seen that a block signal system isprovided in which relays and kindred apparatus are entirely dispensedwith, thus removing all causes and faults arising from the burning orvfusion or other troubles with the contacts. In other words there aredisclosed herein block signal systems which are contactless, it beingunderstood that the switches S of Fig. 2 are perfectly reliable asordinary switches have come to be in the electrical arts, and are notsuch contacts as cause trouble in railway signal systems.

From the fact that alternating current is used the signaling systems maybe operated at an economy obtainable with lone; distance high tensionelectrical transmission. And from the fact that alternating currents areused on the track circuits, no trouble from electrolysis at bond wiresor other points is possible; nor are false signals due to leakage fromother circuits or to earth currents possible since only currents of theproper frequency and of sufiieient energy will operate the motors.

The motors and the transformers, weights and other apparatus at the endof a block and the entrance to the neighboring block may be housedwithin the same semaphore tower base and the motors need be of smallsize and capacity only. There the semaphore arms are operated throughgearing, the motors need only be of a rating of a small fraction of ahorse power; and in the case where the si nal operated is in the natureof a target or disk within a housing, such target or disk may bedirectly connected to the rotor shaft and the motor may be of very smallrating indeed.

- Inasmuch as the number of blocks sup- I other and independentconductors may be provided for the apparatus and will in such case beconnected in circuit as the rails are shown to be connected.

It is to be understood also that lightning arresters may be applied tothe high tension supply circuit and Lo the track circuits and circuitassociated therewith in a manner commonly practised in long distancepower transmission and in the manner practised in connection with thesignal systems heretofore employed.

What I claim is 1. In a signaling system, a plurality of blocks, meansfor impressing alternating current of different phases upon neighboringblocks, home and distant signals, an alternating current motor foroperating said home signal, said motor having windings traversedrespectively by current from the phase circuits of said neighboringblocks, a switch movable with a distant signal for controlling saidmotor through a circuit of one of said blocks, said motor operated inresponse to movement of said switch for moving said home signal toindicate the position of said distant signal.

2. In a signaling system, a plurality of blocks, means for impressingalternating current of different phases upon neighboring blocks, asignal, an alternating current motor for controlling said signal, saidmotor having windings traversed respectively by current from the phasecircuits of said neighboring blocks, a switch controlling said motorthrough one of said block cir cuits, and means responsive to thecondition of a distant block for actuating said switch.

3. In a signaling system, a plurality of blocks, an alternating currentsupply circuit, means for impressing alternating current of differentphases upon neighboring blocks, home and distant signals, an alternatingcurrent motor for operating said home signal, said motor having windingstraversed respectively by current from the phase circuits of saidneighboring blocks, means for reversing said motor, and means responsiveto reversal of said motor for indicating the position of a distantsignal.

4. In a signaling system, a plurality of blocks, an alternating currentsupply circuit, means for impressing alternating current of difl'erentphases upon neighboring blocks, a signal, an alternating current motorfor operating said signal, said motor having windings traversedrespectively by current from the phase circuits of said neighboringblocks, a distant signal, and means controlled thereby for reversingsaid motor to move said first named signal to an indicating position.

5. In a signaling system, a plurahty of blocks, means for impressingalternating current of different phases upon neighboring blocks, asignal, an alternating current motor for controlling said signal, saidmotor having windings traversed respectively by current from the phasecircuits of said neighboring blocks, a switch for reversing said motor,and means responsive to the condition of a distant block controllingsaid switch.

6. In a signaling system, a plurality of blocks, an alternating currentsupply circuit, means for impressing alternating current of difierentphases upon neighboring blocks, a motor, a three position signaloperated thereby, the windings of said motor connected in the differentphase circuits of said neighboring blocks, means for reversmg saidmotor, said signal moved by gravity to one of its indicating positionsand by said motor to its other indicating positions.

7. In a signaling system, a plurality of blocks, an alternating currentsupply circuit, means for impressing alternating current of difierentphases upon neighboring blocks, a motor, a three position signaloperated thereby, the windings of said motor connected in the difierentphase circuits of said neighboring blocks, said signal moved by gravityto one of its indicating positions and by said motor to its otherindicating positions, and means responsive to the movement of a signalof a distant block for reversing said motor.

8. In a signaling system, a plurality of blocks, a polyphase highpotential current supply circuit, means for impressing a low potentialsingle phase current upon each of said blocks, the single phase currentin one block being of displaced phase with respect to the single phasecurrent of a neighboring block, a signal, a polyphase motor foroperating said signal, said motor having windings traversed by currentsfrom the diflerent phase circuits of neighboring blocks, a switch forreversing the current in one of said block circuits for reversing saidmotor, and means responsive to the condition of a distant blockcontrolling said switch.

9. In a signaling system, a plurality of blocks, a polyphase highpotential current supply circuit, means for impressing low potentialsingle phase current upon said blocks, the single phase current in oneblock being of displaced phase with respect to the single phase currentof a neighboring block,

a signal, a polyphase motor for operating said signal, said motor havingwindings traversed by currents from the different phase circuits ofneighboring blocks, and means responsive to the movement of a distantsignal for reversing said motor.

10. In a signaling system, a plurality of blocks, means for impressing asingle phase current on the track circuit of each block, a signal, amotor for operating the same, the single phase currents on neighboringtrack circuits being displaced in phase with respect to each other, saidmotor having a winding traversed by current of one phase from one trackcircuit, and having another winding traversed by current from the phasecircuit of a neighboring track circuit, a three-position switchcontrolling said motor through one of said trackcircuits, and meansresponsive to the condition of a distant block for controlling saidswitch.

11. In a signaling system, a plurality of blocks, means for impressing asingle phase current on the track circuit of each block, a signal, amotor for operating the same, the single phase currents on neighboringtrack circuits being displaced in phase with respect to each other, saidmotor having a winding traversed by current of one phase from one trackcircuit, and having another winding traversed by current of differentphase from a neighboring track circuit, and means responsive to themovement of a distant signal for reversing the current in one of saidneighboring track circuits.

12. In a signaling system, a plurality of blocks, means for impressingalternating current of difierent phases upon neighboring blocks, amotor, a three-position signal moved by gravity to one of its indicatingpositions and controlled by said motor to move to its other indicatingpositions, the windings of said motor traversed by currents from thephase circuits of neighboring blocks, a switch controlling said motorthrough one of said blocks, and means responsive to the condition of adistant block controlling said switch.

13. In a signaling system, a plurality of neighboring track circuitsinsulated from each other, a source of polyphase alternating current,means for impressing a single phase current upon each track circuit, thecurrents in neighboring track circuits being of different phases, asignal, a motor for operating the same, said motor having a windingtraversed by current from one of said track circuits and another windingtraversed by current of a different phase, and a reversing switchcontrollingthe track circuit supplying current to said first namedwinding.

14. In a signaling system, a plurality of neighboring track circuitsinsulated from each other, a source of polyphase alternating i er-.2

current, means for impressing a single phase .current upon each trackcircuit, the currentsin neighboringtrack circuits being of differentphases, a signal, a motor for operating the same, said motor having awinding traversed by current from one of said track circuitsand anotherwinding traversed by current of" a different phase, a reversingswitchcontrolling the track circuit supplying current to said firstnamed winding, andnieans for shifting said reversing switch in responseto the movement of a distant i controlling saidmotor through one of saidsignal circuits, andmeans responsive to the condition of a distantsignal circuit controlling said switch.

16. In a signaling system, a source of. polyphase current, a pluralityof signal circuit sections insulated from each other, both signalconductors of a signal circuit insulated from the correspondingconductors of a neighboring signal circuit, means for impressing asingle phase current upon each signal circuit, the currents inneighboring signal circuits beingdisplaced in phase, a signal, a motorfor operating said signal, said motor having a winding traversed by thecurrent of a signal circuit and another winding traversed by current ofdifferent phase and connected with a neighboring signal circuit, andmeans for reversing said motor in response to the movement of a disannal- 17. In a signaling system, a three-position signal, anelectricmotor for actuating said signalto two of its positions, meansfor deene iL-gizing said motor to allow said signal to be moved bygravity to its third position, a switch controlling said motor, a signalcircuit, and means responsive to the condition of said signal circuit.for actuating said switch.

18. In a signaling system, an alternating current supply circuit,neighboring track circuits insulated from each other, a signal,arotarymagnetic field motor for operating said. signal, a component ofsaid rotary magnetic I field produced by current derived from one trackcircuit, and another .component of said rotary magnetic field producedby current of. different phase from a circuit supplyingcurrent to aneighboring track circuit, and means for reversing said motor controlledfrom a distant track circuit.

19. In a signaling system, an alternating current supply circuit,neighboring track circuits insulated from each other, a signal, a rotarymagnetic field motor for operating said signal, a component or saidrotary netic field produced by current derived from one track circuit,and another component of said rotary magnetic field produced by currentof different phase, and means for reversing said motor in response tothe move ment of a distant signal.

20. In a signaling system, an alternating current supply circuit,neighboring track circuits insulated from each other, a signal, a rotarymagnetic field motor for operating said signal, a component of saidrotary magnetic field produced by current derived from one trackcircuit, and another component of said rotary magnetic field produced bycurrent or different phase, means for reversing said motor in responseto the movement of a distant signal, said first named signal moved to adifi'erent position for each direction of movement of said motor andoccupying a third position in response to the action of gravity.

21. In a signaling system, an alternating current supply circuit, asignal, an induction motor for operating said signal, a primary windingof said motor traversed by current derived from a track circuit, anotherprimary winding traversed by current of different phase supplieddirectly thereto independently of a track circuit, a switch controllingthe direction of current in said first named winding, and meansresponsive to the condition of a distant track circuit con trolling saidswitch.

In a signaling system, a three-position signal, a plurality ofneighboring signal circuits, means for impressing alternating currentsof different phases upon neighboring signal circuits, a polyphase motorderiving current from neighboring signal circuits controlling movementof said signal to two of its positions, said signal being moved to itsthird position by gravity, a three-position switch controlling saidmotor through a signal circuit, and a distant three-position signal,said switch taking a different position for each different position ofsaid distant signal.

23. In a signaling system, a three-position signal blade biased towardone position, means for mechanically actuating the same to and forholding the same in the other positions comprising a polyphase motor,signal circuits for neighboring blocks, means for impressing currents ofdifferent phases upon signal. circuits of neighboring blocks, said motorderiving current from said means, and the current of one phase of saidmotor derived through one of said signal circuits.

24-. In a signaling system, a third-position signal blade biased towardone position, means for mechanically actuating the same to and forholding the same in the other positions comprising a polyphase motor,neighboring signal circuits, means for impressing currents of differentphases upon neighboring signal circuits, said motor deriving currentfrom said means, and the current of one phase of said motor derivedthrough one of said signal circuits, a switch for reversing said motor,and means responsive to the condition of a distant signal circuitcontrolling said switch.

25. In a signaling system, the combination with a plurality of blocks,of a signal blade for each block adapted to take three indicatingpositions and biased toward one of them, means for impressing current ofdifferent phases upon neighboring blocks, a motor for actuating saidsignal blade to two of its positions and deriving current from saidmeans, the current of one phase delivered to said motor derived throughone of said blocks, said motor de'e'nergized in response to the presenceof a vehicle in a block whereby said signal moves to its third positionto which it is biased, and a switch controlling the motor associatedwith a signal blade of another block controlled by said first-namedmotor.

CORNELIUS D. EHRET.

WVitnesses WM. HAMILTON, EDITH N. BAHN.

Copies of this patent may be obtained for five cents each, byaddressingthe Commissioner of Patents.

Washington, I). 0.

